In general, a microphone is a device converting sound into an electrical signal, and used for mobile communication devices such as a terminal, and various communication devices such as an earphone or a hearing aid. Such a microphone requires high audio performance, reliability, and operability.
A capacitive microphone based on microelectromechanical system (MEMS) (hereafter simply referred to as a “MEMS microphone”) has high audio performance, reliability, and operability, as compared with an electret condenser microphone (hereafter simply referred to as an “ECM microphone”).
The MEMS microphone is classified into a non-directional (omnidirectional) microphone and a directional microphone, depending on the directional characteristics.
The non-directional microphone has uniform sensitivity for sound waves traveling inside in all directions.
On the other hand, the directional microphone has different sensitivity depending on the directions of incident sound waves, and falls into a unidirectional type and a bidirectional type in accordance with the directional characteristics.
For example, the directional microphone is used for recording in a narrow room or capturing only desired sounds in a room with a lot of reverberation.
When these microphones are mounted in a vehicle, sound sources are far from them and noise is variably generated due to the environmental characteristics of the vehicle. Thus, there is a need for a microphone that is strong against changes in the noisy environment inside the vehicle, and for this purpose, the directional MEMS microphone that captures sounds only in desired directions is used.
However, since the directional microphone of the related art captures sounds only in desired directions, it is strong against noise, but the sensitivity is low and the frequency response characteristic is poor compared with the non-directional microphone.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention, and therefore, it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.